An object of this invention is to provide a band distribution inspecting device and band distribution inspecting method capable of carrying out inspection on whether or not a scattered oscillation signal oscillated containing a frequency variation from the fundamental frequency with the fundamental frequency as a reference point has a band distribution rapidly, with a simple way and at a cheap price. A scattered oscillation signal SSS inputted to a band distribution detecting section 22 is outputted as a predetermined band pass signal SBP through a band pass filter 17 having a predetermined pass band of a predetermined narrow-band width Δf within a band distribution. This signal is converted to a root-mean-square value by a smoother 19, smoothed by a capacitor C1 and transferred to a general purpose inspecting device 21 as a DC signal SAV. The DC signal SAV is compared with a predetermined voltage value VX by a comparator 25 and its comparison result is judged by a judging section 25 and then, an inspection result is outputted as a judging signal J. As a result, an edge frequency in the band distribution of the scattered oscillation signal SSS and disturbance of frequency variation within/out of the band and dullness in waveform and the like can be inspected for.